#!/usr/bin/node
const Writable=require('stream').Writable;
function GreenStream(){
  Writable.call(this);

  this._write=(chunk,encoding,callback)=>{
    process.stdout.write('\033[1;32m' + 'hello world!' + '\033[1;37m');
    callback();
  };
  
}
GreenStream.prototype=Writable.prototype;
let rs=new GreenStream();
process.stdin.pipe(rs);
